8-12aas Battery Pack

[m8ex]

I have heard of the battery problem. So i gona make a battery pack with something like 8-12AAs and a LM2575 or a LM2574 (step-down thingy). But i'm not sure if the dc-in is 3.3V or 3.0V and is the possible to play games with the power connector sticking out to the right? What size is the connector? Is 500mA enough to power the gp2x or should i use the LM2475 that have 1000mA?

 

[BradN]

3.3V, go for the 1000mA one (and you may want a heatsink), and there's varying reports of annoyance with the plug where it is. Not sure of the connector size, you'll have to experiment, or maybe the wiki has info. I think regulators like that can be more efficient with an input voltage closer to the target voltage, so I would do groups of 4 in parallel, or groups of 6 if you plan on making it 5V capable for peripherals in the future

Also, there's supposedly two 3.3V pins on the EXT connector, so I'm guessing if the DC in spot bothers you, you might be able to make it work with the EXT connector. I'm not sure how many amps the pins on there are rated for though, but with 4 pins total (positive and ground), it's probably ok, and it shouldn't need as many amps at 3.3V as it does from the internal batteries.

 

[Mentor]

you don`t need any stepdown devices, just have your cells wired in two`s together and then in series, and since people can play with the mains adapter plugged in then it shouldn`t be a problem for you eitther, the voltage from two cells is going to be right since thats what the device holds.

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dire ascii "wiring" diagram for 8 cells included <_< , lines are wires and [] is a cell.

Mentor.

 

[BradN]

Problem is I'm not sure if the 3.3V input bypasses the internal step-up regulator - if it does, the 3.3V chips sure aren't going to run on 2.4V, much less under 2.4V near the end of the discharge cycle (assuming rechargeable NiMH/NiCD cells). It might work for a while on 3.0V from alkalines, but once the batteries discharge a little, you won't get a full 1.5V from each, and 3.0V is already at the bottom end of acceptable voltage for lots of 3.3V chips.

 

[LIZARDKING]

I bought a RadioShack 3V 500mA and used it 5-6 times @ 30mins each time w/ no problems....

 

[BradN]

Hmm, I checked the datasheet for LM2575, and it looks like it wants 7V minimum input from the example at least. Better check the datasheets before committing to any given design.

 

[m8ex]

I thought about the EXT thing but is that directly connected to the DC in? Can somebody measure the resistance between pin 20/21 and DCin+ and pin 13/24 and DCinGND(both ways). I dont have mine yet so i can't do it.

 

[Mentor]

if the 3v in does bypass the regulator then maybe you could swap to using lithium polymer batteries, you need to get the correct rated cells and the right type of charger (or they explode), but they have insane storage capacities for their size and are rated at 3.6v per cell iirc so you should be able to use em straight off , the only downside is you MUST make sure they can`t discharge below 3.0v or it destroys the cell, so you need a circuit to make sure you can`t run em totaly flat by cutting the power when it gets too low.

example of cells (note max physical size and capacity)
Lithium polymer cells example

and wiki on same subject
wikki


Mentor.

 

[m8ex]

I found a batteryholder for 8 AAs so i gona use 8x2400mAh batteries. That is 9.6V and well above the needed 7.0V even when the voltage drops to 1.1v on each cell (8.8V).

 

[nubie]

I have heard of the battery problem.

​

What battery problem?

Seriously, if you play longer than 4 hours straight without a break, then yes there is a problem, but not with the batteries

I get routinely 4-5 hours out of 2 2500mAh NiMH.

That's just fine in my book, there's not that much time to play in a day anyway.

I would suggest using NiMH batteries that are high quality, use a really fine grit sandpaper to clean off the battery terminals, and use a drop of that super-fluid that improves electrical conductivity (you can find it at high-end audio shops).

If you really need more power, hold on, I am searching the forums now for some 13,000mAh cells that were mentioned, just use something like the GBA adapter and run the power straight to the battery holder, then it is out of your way when playing.

Edit: Vimacs found 13,000mAh, this is the old battery pack thread.

Seriously though, if it can be done on only 2 cells without a voltage regulator, it is better.

For a start all cells have differing voltages, which makes 2 cells better than 8 for energy release and long life.

Secondly, the voltage regulator is not 100% efficient, so you are wasting more power.

 

[Mr. Anderson]

I get 10 hours of music playback(@100mhz) about 5 hours video and 5-6(4 hours with 266mhz and 6 with 200)hours emulation out of my 2600mAh batteries

 

[nubie]

Or, you could try two of these High capacity AAA - D size

The C size go to 4,000mAh (aka 4 Amp)

20 of them would be about $70 or 40 Pounds.

you could use them to play for about 7-8 hours.

The D cells would likely last over 15 hours.

That is just with 2 cells connected straight.

 

[m8ex]

Seriously, if you play longer than 4 hours straight without a break, then yes there is a problem, but not with the batteries

ok i have a problem. (step #1)
it's maybe was a bad idea. But i just want more than 4h game time.
Those 1,3Ah batteries were pretty 'sexy'

 

[triton]

that wasnt 1.3A that was 13A! that batt was probably 2x the size of a D cell!

 

[nubie]

Seriously, if you play longer than 4 hours straight without a break, then yes there is a problem, but not with the batteries

ok i have a problem. (step #1)
it's maybe was a bad idea. But i just want more than 4h game time.
Those 1,3Ah batteries were pretty 'sexy'

​

You mean 13Ah right

 

[BradN]

There's more efficient switch mode regulators than the ones originally mentioned, if you look for voltage regulators on digikey.com - some were in excess of 90%, but might require slightly more external circuitry. But hey, if you're going for a long life battery pack...